DEAR HARRIETTE: I have a friend who is a know-it-all. As we are talking and catching up, she regularly interrupts me to explain that she knows whatever the subject is already and gives an example. Rarely do I get a whole sentence out before she jumps in to put her personal stamp all over it. This is irritating, to say the least. I know she is smart and busy in her life. She has had tons of experie…